Aluminum working procedure



United States Patent 3,266,945 ALUMINUM WORKING PROCEDURE Werner Helling, Munich, and Hans-Friedrich Honsel, Meschede (Ruhr), Germany, assignors to Honsel-Werke Aktiengesellschaft, Meschede (Ruhr), Germany No Drawing. Filed Aug. 7, 1962, Ser. No. 215,259 Claims priority, application Germany, Aug. 10, 1961, H 43,377; June 28, 1962, H 46,212; July 13, 1962,

11 Claims. (Cl. 148-115) This invention generally relates to aluminum products and is particularly directed to a method of forming aluminum bodies of aluminum of a purity of 99.8 to 99.99% and of aluminum magnesium alloys up to 2.8% magnesium on the above mentioned base which may be imparted with a glossy surface of high luster and brilliance.

The term aluminum body as used herein is deemed to refer to aluminum sheets, aluminum bands or strips, aluminum wires, and the like shapes into which aluminum may be formed by various metal working procedures such as rolling, drawing and the like.

The aluminum bodies of this invention are suitable for the production of aluminum articles with pronounced surface brilliance and may successfully be subjected to decorative anodic oxidation.

With a view to producing aluminum articles with decorative or ornamental effect, aluminum bodies are customarily first imparted with a surface gloss by means of chemical or electrochemical processes whereafter the shiny surface is covered or plated with an anodic cover layer. This procedure is generally known as gloss or burnish anodizing or eloxation (hereinafter referred to as anodizing).

It is well known in the art that the metallographic structure and lattice arrangement of the aluminum is a decisive factor with respect to the attainment of satisfactory luster and smoothness of the completed aluminum article. A heterogeneous lattice structure which, for example, in addition to the mixed crystals of aluminum contains extraneous compounds such as Al Fe, MggSi or the like, yields opaque cover layers upon anodizing. By contrast, a homogeneous structure or lattice formation wherein the additives and alloying components are integrally built into the aluminum lattice exhibits, upon anodizing, more glossy and attractive surface characteristics.

According to the prior art procedures, cast aluminum billets or ingots usually of circular cross section are customarily used as raw material for the production of strips, sheets, wires and the like aluminum bodies to be subjected to anodizing. The billets are first annealed (homogenized) at relatively high temperatures. The homogenisation procedure is usually performed for a period of about ten hours, wherea-fter the billets are slowly cooled to room temperature. The annealed and cold billets are then again heated in inductive manner to about 400 C. and at this temperature, the billets are then pre-shaped, for example, compressed into rails, relatively thick wires or rods, and the like shapes. These intermediate shapes are thereafter rolled into strips or are drawn to the desired thickness. This prior art procedure which has generally been adopted by the industry is relatively cumbersome and expensive, and oftentimes does not yield surfaces with satisfactory brilliance.

It is therefore a primary object of this invention to overcome the deficiencies of the prior art process referred to and to provide a process which conditions the metallographic structure of the aluminum bodies so that upon subsequent anodizing, superior surface characteristics with regard to luster and gloss are obtained.

It is also an object of this invention to provide a process for forming and conditioning aluminum bodies which is simple to carry out at a minimum of expenditure.

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Generally it is an object of this invention to improve on the art of imparting high gloss and luster to aluminum surfaces.

The present invention is based on the realization that aluminum bodies may be imparted with glossy surfaces of superior characteristics by drastically reducing the time period within which the hot aluminum billet remains within certain critical temperature ranges during the shaping procedure into aluminum bodies.

Briefly, and in accordance with one embodiment of this invention, it has been ascertained that aluminum bodies having extremely brilliant and glossy surfaces are obtained in economic and simple manner by proceeding in the following manner: An aluminum ingot or billet is first homegenized according to the prior art, whereafter the bot billet is quenched to a temperature of about 500 C. The thus quenched billet is then worked within the temperature range of about 500 to 420 C. into an intermediate shape. Thus, for example, the billet may be rolled into sheet form, and this intermediate shape is thereafter further quenched to temperatures of below about 200 C. The final shaping, for example, cold rolling into sheets, strips and the like, is then performed at this temperature.

By twice quenching the hot ingot or billet in the indicated manner, the temperature ranges which negatively affect the brilliance of the final product are rapidly overcome and the two-stage quenching procedure as outlined above thus effectively reduces the temperature to values which no longer detrimentally affect the final luster. In order to form the intermediate shapes, the hot billet has, of course, to be maintained for a short period within the critical temperature range, but this period should be as short as possible, so as to reduce the detrimental effect. Extensive experiments have conclusively established that the inventive quenching procedure with the resulting sudden temperature decrease of the annealed billet considerably improves the fina-l luster.

In adapting the inventive concept to the production of glossy aluminumiwires, the'billet, after the initial anhealing to homogenize the product and after the first quenching to 500 C., is compressed into rods of'inte'rmediate thickness, for example, of a diameter of about 10 mm. within the indicated range of 500 to'420 C. Upon further quenching to a temperature below about 200, the rods are then cold drawn to a diameter of desired thickness.

According to the invention, it has been ascertained that the initial homogenisation step is advantageously carried out at temperatures of about 580 to 620 C. An optimumtemperature value is about 600 C.

The quenching steps may be effected by immersing the billet in water which may be enriched with small quantities, for example, 1 to 2% of nitric acid.

It has also been found that the final cold rolling or cold drawing of the intermediate shapes into the final shape should be performed without-further intermediate annealing. jI-f desired, the stability of the final product may be increased by temper-anne aling to a temeprature of about to 200 C.

As previously mentioned, quenching with water, preferably with small additions of nitric acid, is particularly suit-able. However, quenching oils can also be used.

With a view to obtaining particularly favorable results, it is advantageous that the initial quenching of the annealed billet is per-formed so as to obtain a rapid and uniform cooling throughout the entire cross section of the billet. Such rapid and uniform quenching is difli cult to perform on circular billets wherein the ratio between surface area and volume is very small. In such billets, the core or interior portion tends to remain hot for a relatively long period of time during the quenching operation. For this reason, it is recommended to use billets having a relatively large ratio of surface to weight. Experiments have established that excellent results are obtained if billets are used wherein the ratio of weight to surface is smaller than 2.2 (kg/dmF). Such a ratio, for example, prevails in a billet which has the following dimensions:

Thickness 12 Width 80 Length 140 The inventive method can be successfully performed with aluminum of varying purity. Thus, for example, aluminum having an aluminum content of 99.7 to 99.9%, that is, very pure aluminum, is eminently suitable for the inventive method. However, aluminum alloys as, for example, magnesium aluminum alloys having a magnesium con-tent of, for example, 0.2 to 2.8%, may also be treated in the inventive manner with excellent results.

The invention will now be described by an example, it being understood, however, that this example is given by way of illustration and not by way of limitation and that many changes may be effected without affecting in any way the scope and spirit of this invention as recited in the appended claims.

Example A cast aluminum billet having an aluminum content of 99.83% was homogenized at a temperature of 600 C. The annealing was carried out for a period of eight hours. The hot billet was then quenched with water con taining 1.5% of nitric acid to a temperature of 500 C. The ratio weight to surface of the billet was 2.1 (kg./dm. and the quenching was performed so that the billet was chilled rapidly and uniformly throughout its thickness. When the billet had reached a temperature of 500 C. it was rolled in a rolling mill into plates of about half an inch thickness. During the rolling, the temperature of the billet decreased to about 440 C. After the rolling, the plates were tfiurther quenched in water to a temperature of 100 C. and were then cold rolled into a final layer thickness of one-tenth of an inch. The sheets thus obtained could be imparted with a high surface luster, for example, by anodizing.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing trom such principles.

What is claimed is: 7 v

1. A method of forming aluminum bodies from aluminum billets containing 99.8 to 99.99% of aluminum and aluminum billets containing up to 2.8% of magnesium, which comprises homogenizing the billet at a temperature above about 550 C. and below the cfusi-on point, quenching the homogenized billet to a temperature of about 500 C., thereafter immediately shaping the billet into an intermediate shape in a temperature range of about 500 to 420 C., then quenching the intermediate shape to a temperature of below about 200 C. and shaping the intermediate shape into a final aluminum body at a temperature below 200 C.

2. A method as claimed in claim 1, wherein saidshaping operations are efiected substantially immediately after said quenching operations.

3. In a method of forming aluminum bodies from an aluminum billet, wherein the billet is first homogenized and is thereafter shaped into bodies, the improvement comprising, in combination therewith, the steps of conditioning the metallographic structure of the bodies to a state in which surfaces of high brilliance can be imparted to the body, by first quenching the homogenized billet to a temperature of about 500 C., thereafter immediately shaping the quenched billet within a temperature range of about 500 to 420 C. into an intermediate shape, then further quenching the intermediate shape to a temperature of about below 200 C., and finally shaping the intermediate shape into a final aluminum body at a temperature below 200 C.

4. A method of :forming aluminum bodies from an aluminum billet and conditioning the metalloglraphic structure of the bodies to improved their surface characteristics, which comprises homogenizing the aluminum billet at a temperature of about between 580 to 620 C., quenching the hot billet to a temperature of about 500 C., immediately thereafter shaping the quenched billet within a temperature range of about 500 to 420 C. info a first shape, quenching said first shape to a temperature of below about 200 C. and then finally shaping said first shape into a final shape.

5. A method as claimed in claim 4, wherein said quenching is performed with water.

6. A method as claimed in claim 5, wherein said water contains a small amount of nitric acid.

7. A method as claimed in claim 4, wherein the ratio of weight to surface of the billet is less than 2.2 (kg./drn.

8. A method of working flat aluminum bodies from an aluminum billet which comprises homogenizing aluminum billet to a temperature in excess of 550 C., substantially uniformly and rapidly quenching the billet to a temperature of about 500 C., immediately thereafter rolling the billet into plates within a temperature range of about between 500 to 420 C., quenching the plates to a temperature of below about 200 C. and cold rolling the plates into a flat aluminum body.

9. A method of producing aluminum wire from an aluminum billet which comprises homogenizing the aluminum billet at a temperature in excess of 550 C., so stantially uniformly and rapidly quenching the billet to a temperature of about 500 C., immediately thereafter drawing the billet into rods within a temperature range of about 500 to 420 C., quenching the rods to a temperature below about 200 C. and then cold drawing the rods into thin wire.

10. A method as claimed in claim 8, wherein said flat body is recovery annealed to a temperature of between about to 200 C.

11. A method as claimed in claim 9, wherein said Wire is recovery annealed to a temperature of between about 100 to 200 C.

References Cited by the Examiner UNITED STATES PATENTS 662,951 12/ 1900 Mach 14811.5 1,931,912 10/1933 Whitzel 14811.5 1,931,913 101/933 Ennor 148-11.5 2,262,696 11/194-1 Nock et a1. 1481-1.5 3,180,806 4/ 1965 Hollingsworth 20429 FOREIGN PATENTS 780,570 8/ 1957 Great Britain.

HYLAND BIZOT, Primary Examiner.

DAVID L. RECK, Examiner.

W. B. NOLL, H. F. SAITO, Assistant Examiners. 

1. A METHOD OF FORMING ALUMINUM BODIES FROM ALUMINUM BILLETS CONTAINING 99.8 TO 99.99% OF ALUMINUM AND ALUMINUM BILLETS CONTAINING UP TO 2.8% OF MAGNESIUM, WHICH COMPRISES HOMOGENIZNG THE BILLET AT A TEMPRATURE ABOVE ABOUT 550*C. AND BELOW THE FUSIION POINT, QUENCHING THE HOMOGENIZED BILLET TO A TEMPERATURE OF ABOUT 500*C., THEREAFTER IMMEDIATELY SHAPING THE BILLET INTO AN INTERMEDIATE SHAPE IN A TEMPERATURE RANGE OF ABOUT 500 TO 420*C., THEN QUENCHING THE INTERMEDIATE SHAPE TO A TEMPERATURE OF BELOW ABOUT 200*C., AND SHAPING THE INTERMEDIATE SHAPE INTO A FINAL ALUMINUM BODY AT A TEMPERATURE BELOW 200*C. 